Materials with elastic range and the possibility of stress oscillations in pure shear

The framework of a general theory of materials with elastic range [6] is used to show that, for an isotropic material undergoing a process in which the difference (D - DP) between the total and the plastic rate of derformation is uniformly small, the incremental constitutive equation features an isotropic dependence of the Jaumann derivative, of the Cauchy stress T on (D - DP). thus, it is argued that stress oscillations in pure shear should be seen as a (not desired) consequence of the choice made for the hardening rule rather than, as was also conjectured, of the choice made for the invariant time derivative of T to appear in the constitutive equation.